Flameless Igniting Slurry Composition and Method of Preparing

ABSTRACT

A flameless igniting slurry composition has an oxidizer, a fuel, a flame retardant, a liquid, and a rheology modifier. The rheology modifier and the flame retardant may be in particulate form. The flame retardant may be a water-soluble salt. The liquid may be water. The oxidizer may be potassium nitrate. The fuel may be silicon and charcoal. The composition may consist of on a mass basis 25-50% oxidizer, 20-30% fuel, 2-5% flame retardant, and 0.5-10% rheology modifier. The invention may be a device consisting of a shape of absorbent web material impregnated with the composition in a dried state. The invention may be a device consisting of the composition in a dried, particulate form. A process for producing the composition is also disclosed.

FIELD OF THE INVENTION

The present invention relates to a pyrotechnic composition that is useful as a first fire or igniting composition, and is more particularly concerned with easily ignitable and flashless, non-explosive intermediate items, commonly referred to as “first fire,” “igniters,” and “starters.” These items light the main pyrotechnic filling safely, but also reliably and easily. The term “first fire” would semantically and logically appear to apply to the prime ignition element, but in pyrotechnics, the term refers to the intermediary ignition source between the primary ignition item and the main explosive item. The terms “starter mixture” or “ignition mixture” are used occasionally in the same sense.

BACKGROUND OF THE INVENTION

First fire formulas appear sporadically in the patent literature, occasionally claiming unusual compounds and alloys as fuels, but generally being in line with formulas and work done in a few patented ignition mixtures. A notable example is U.S. Pat. No. 1,805,214 granted to H. C. Hale in 1931 for work performed at Picatinny Arsenal, which was the first use of low-gassing mixtures as starters. Additional early examples include U.S. Pat. Nos. 2,421,029; 2,497,387; 2,640,770; 2,643,946; 2,709,129; 2,726,943; and 2,726,944.

The first fire or igniting composition must invariably be easily ignited by the primer or powder flash, and yet be neither friction nor impact sensitive to a degree that would cause the composition to be hazardous for safe manufacturing. This requirement means the composition must have a sufficiently low ignition temperature. It has been found that the ignitability of gasless thermite-type starters depends on several factors. These include the nature of the oxidizable metal powder and the oxidizing agent, the particle size of the composition's ingredients, and the nature of any other components of the composition. To ensure ignition of the starter mixture, the preferred particle size of the starter composition is sufficiently small to permit all of the composition material to pass through a No. 200 U.S. Standard Sieve, with the majority of the composition material also being capable of passing through a No. 325 U.S. Standard Sieve.

The first fire or igniting composition must dependably ignite the explosive filling. The work disclosed in U.S. Pat. Nos. 2,640,770 and 6,739,621 B2 shows that a starter that produces slag and evolves little or no gas more reliably ignites the filling than a starter that evolves gases and builds up pressure in a confined space.

Explosive filling compositions with high ignition temperatures (i.e., above 600° C.) can be difficult to ignite using solely the “spit” from a black powder fuse or similar mild ignition stimulus. In such situations, an initial charge of a more-readily-ignitable material, called a “first fire,” is frequently used. The requirements for such a mixture include:

1. Reliable ignitibility from a small thermal impulse such as a fuse. The ignition temperature of a first fire should be 500° C. or less.

2. The first fire mixture should attain a high reaction temperature, well above the ignition temperature of the main filling composition. Metal fuels are usually used in the “first fire” mixture when high reaction temperatures are needed.

3. A first fire mixture that forms a hot, liquid slag reaction product is preferred. The slag creates considerable surface contact with the main filling composition, facilitating the filling composition's ignition. The production of hot gas by the first fire mixture will usually produce good ignition behavior of the main filling composition on the ground, but the reliability of the first fire mixture's ability to ignite the main filling composition deteriorates at higher altitudes where cooler environmental conditions exist. Production of liquid and solid reaction products by the first fire mixture provide better heat retention compared to hot gas, which aids ignition of the main filling composition at higher altitudes.

4. A slower-burning first fire mixture is preferred over one that reacts more rapidly. The slower release of energy enables better heat transfer to the main composition. To reduce the reaction rate, most “first fires” are pressed into place or added as moist pastes that harden on drying instead of being introduced as faster-burning loose powders.

The requirements for a successful first fire mixture are surprisingly stringent. The first fire mixture must be easy to ignite by the initiator's output and generate a large amount of heat, but not too rapidly or violently. A violent reaction may cause the first fire to detach from the surface of the main filling composition and failed to ignite the main filling composition. It is advantageous for the first fire mixture to produce some non-volatile products that leave a hot slag that efficiently transfers the heat generated by the exothermic reaction of the first fire mixture to the main filling composition. The components of the first fire mixture must also be compatible (i.e. nonreactive) with those of the main filling composition since the first fire will be either pressed as a final layer, or laid on the surface of, the main filling charge. Finally, the first fire composition should not be too sensitive and should have a reaction product that ignites the main filling composition with relative ease. This is achieved by three types of compositions:

Gunpowder and its Variants: This composition type is ignited very easily by a flash and has a suitable reaction product of hot particles pressurized by hot gases. A popular method of employing gunpowder is by impregnating gunpowder in cambric, a fine, dense cloth, or other type of absorbent web.

Organic Compounds: This composition type, which generates a reaction product that is generally much cooler than gunpowder, is an organic compound plus an oxidant. A good example of this type of compound is a 60/40 composition of potassium nitrate and lactose. This compound is commonly used to ignite colored smoke compositions where an excessively hot first fire could cause the main smoke-generating composition to catch fire and spoil the desired effect.

Slag Producers: This composition type produces the hottest reaction products. Compositions of this type are excellent igniters and are formulated either from fuel elements with a salt oxidizer or from thermite materials (a metal fuel element combined with a metal oxide). Table 1 gives examples of the thermite type of first fire compositions.

TABLE 1 Slag Producing First Fire Compositions Composition Uses B/KClO4/Thiokol General Priming B/KNO3 High Altitude Flare Ignition Mg/BaO2/C Tracer Ignition Al/Si/KNO3/Fe3O4/C HC Smoke Ignition Si/PbO2/Cu2O Phosphorus Ignition Si/Ti/Pb3O4 Delay Ignition

Potassium nitrate is frequently used in igniters and first fires. Compositions made with this oxidizer tend to have low ignition temperatures (typically below 500° C.), and yet the mixtures are reasonably safe to prepare, use in production, and store. Potassium chlorate formulations also tend to have low ignition temperatures, but they are considerably more sensitive (and hazardous). Known heat-producing mixtures, as disclosed in British Patent No. 627,678 or U.S. Pat. No. 3,025,153, indicate nitrates, chlorates, and manganese or iron oxides are suitable oxidizing agents.

It has been discovered that a very good exothermic composition may be formulated using elemental silicon as fuel to replace more sensitive and violent burning magnesium or aluminum. It is important that the silicon employed should have a small particle size. Maintaining other variables constant, it is generally true that the smaller the silicon particle size, the more reactive the particle becomes. Generally, it is found preferable that the silicon particles used in such an exothermic composition should be so small that at least 50% and preferably, 75% of them will pass through a No. 200 U.S. Standard Sieve. It is known that mixtures of silicon and potassium nitrate are capable of reacting exothermically when they are strongly heated, but they cannot be used as fuse compositions since they are incapable of propagating the reaction progressively through a train of small cross sectional area. U.S. Pat. No. 2,497,387 discloses the use of red lead together with potassium nitrate as oxidizing agents and silicon as fuel to overcome this drawback. However, red lead's toxicity

Charcoal is another organic fuel, which has been employed in high-energy mixtures for over a thousand years. Charcoal is frequently the fuel of choice when high heat and gas output as well as a rapid burning rate are desired. The addition of a small percentage of charcoal to a sluggish composition will usually accelerate the burning rate and facilitate ignition.

A pyrotechnic composition will usually contain a small percentage of an organic polymer that functions as a binder, holding all of the components together in a homogeneous blend. These binders, being organic compounds, will also serve as fuels in the mixture. Without the binder, materials might well segregate during manufacture and storage because of variations in density and particle size. The granulation process, in which the oxidizer, fuel, and other components are blended with the binder (and usually a suitable solvent) to produce grains of homogeneous composition, is a critical step in the manufacturing process. The solvent is evaporated following granulation, leaving a dry, homogeneous material, which can be either pelletized or used in an unaltered state. Common binders include nitrocellulose (with acetone as the solvent), polyvinyl alcohol (used with water as the solvent), and laminac (an unsaturated polyester cross-linked with styrene—the material is a liquid until cured by catalyst, heat, or both, and no solvent is required). Epoxy binders can also be used in liquid form during the mixing process and then allowed to cure to leave a final, rigid product.

Numerous safety regulations take into account the hazards associated with the production of pyrotechnics. Accordingly, the components of pyrotechnical mixtures are listed according to degrees of hazardousness in the accident prevention regulations issued by social insurance institutions that seek to prevent occupational accidents. These regulations demand graded safety precautions in the production of pyrotechnic mixtures. The two most hazardous groups, oxidizer and fuel, may no longer are mixed by hand. They are mixed automatically behind protective walls or in separated rooms, which are closed off from the control room by an explosive-resistant wall. This type of production is usually called “working under security.” This requirement applies primarily for dry powdery components. If measures are taken during the mixing to reduce the ignitability and the mechanical or thermal sensitivity of the resulting mixtures, a reduction in the hazardousness grading can be achieved. One such measure is to mix the components together with a liquid instead of in the dry state. This method is used particularly during the mixture of pyrotechnical igniting mixtures. By adding solvents such as water, pyrotechnical igniting mixtures can be produced with considerably fewer hazards than when the components are in the dry state.

For the same safety reason mentioned above, a water-bearing slurry or paste composition comprising essentially an inorganic oxygen-supplying salt, a fuel, a surface-active agent, and water can be used as the preferred solvent carrier. Many thickener/surfactant/dispersant or gelling agents are known that have been employed with varying degrees of success, either alone or in combination, in water-bearing slurries. Examples of these include galactomannan polysaccharide guar gum, pregelatinized starches, hydroxyethylcellulose, carboxymethylcellulose, tamarind seed flour, and hydrophilic vinyl polymers, such as polyacrylamide. The most widely used of these thickening agents have been the galactomannan, particularly guar gum, which has been known as a binder and granulating agent for many years as disclosed in U.S. Pat. Nos. 3,617,407; 3,984,342; 4,128,443; and U.S. Patent Publication No. 2009/0314397.

Such a pyrotechnic ignition composition or device made using a water-bearing slurry or paste is useful when the pyrotechnic composition is used to impregnate a shape of absorbent web material such as lightweight cotton cloth (cambric), uncoated fiberglass, and open cell foams. Any shape, normally dictated by the end use, can be employed. Typically, such shapes include cup shapes, cylindrical shapes, hemispherical shapes, rectangular shapes, etc.

Pyrotechnical igniting mixtures are mixtures of solid matter in mostly the powdery state whose components consist mainly of reducing agents and oxidizing agents. When a sufficient quantity of energy is supplied, e.g. in form of an igniting flame, an oxidation-reduction process is initiated: the pyrotechnical mixture will burn away more or less intensely depending on the mixture's composition and arrangement.

Pyrotechnical igniting mixtures have numerous uses and are used, for example, as igniting heads of matchsticks, in flare and signal ammunition, in smoke and cloud bodies, in gas generators, e.g. for safety airbags, and in numerous other arrangements in fireworks bodies.

A major drawback of using such mixtures is the hazard created by the creation of a flame front at the moment of ignition of the main filling composition. For example, a smoke grenade has been observed to emit a flame front with a height of approximately 4-10 inches through the grenade's emission ports. The flame front was observed to last from 1-5 seconds while the smoke charge began burning. This behavior can create safety hazards to personnel and equipment, as well as potentially causing brush and grass fires in dry environments with significantly elevated fire danger conditions.

Therefore, a need exists for a new and improved flameless igniting slurry composition that provides a first fire igniting composition or starter, which meets all requirements for a satisfactory starting material while also controlling the composition's ability to produce a flame. In this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the flameless igniting slurry composition according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides a composition primarily developed for the purpose of providing a first fire igniting composition or starter, which meets all requirements for a satisfactory starting material while also controlling the composition's ability to produce a flame.

SUMMARY OF THE INVENTION

The present invention provides an improved flameless igniting slurry composition, and overcomes the above-mentioned disadvantages and drawbacks of the prior art. As such, the general purpose of the present invention, which will be described subsequently in greater detail, is to provide an improved flameless igniting slurry composition that has all the advantages of the prior art mentioned above.

To attain this, the preferred embodiment of the present invention essentially comprises a composition of an oxidizer, a fuel, a flame retardant, a liquid, and a rheology modifier. The rheology modifier and the flame retardant may be in particulate form. The flame retardant may be a water-soluble salt. The liquid may be water. The oxidizer may be potassium nitrate. The fuel may be silicon and charcoal. The composition may consist of on a mass basis 25-50% oxidizer, 20-30% fuel, 2-5% flame retardant, and 0.5-10% rheology modifier. The invention may be a device consisting of a shape of absorbent web material impregnated with the composition in a dried state. The invention may be a device consisting of the composition in a dried, particulate form. A process for producing the composition is also disclosed. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims attached.

There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of the manufacturing process for the current embodiment of the flameless igniting slurry composition constructed in accordance with the principles of the present invention.

The same reference numerals refer to the same parts throughout the FIGURE.

DESCRIPTION OF THE CURRENT EMBODIMENT

An embodiment of the process for manufacturing a flameless igniting slurry composition of the present invention is shown and generally designated by the reference numeral 10.

The invention relates to a composition and method for producing aqueous slurry or paste mixtures based on: oxidizer, fuel, flame suppressant additive and rheology modifier. The mixture can be used to impregnate an absorbent web material, such open cell foam, with the ignition composition of this invention for use as ignition device after drying. Alternatively, the paste or slurry can be dried to remove the liquid and obtain a solid product, which can then either be used as an ignition device in that state or rendered into particulate form.

In general, flame suppressant/flame retardant compounds act in one of two ways: either by preventing ignition of a product or by preventing the spread of a fire once a product is ignited. First, the ignition susceptibility of a product is lowered when the flame retardant increases the net heat capacity of the product. Second, once a fire has already begun, flame retardants can reduce the tendency of the fire to spread by reacting with the product and forming a less flammable char or noncombustible gaseous layer along the boundary of the fire. Within these two general flame-retardant mechanisms, Kirk-Othmer's Encyclopedia of Chemical Technology (Kirk-Othmer, 2001) provides a more detailed summary of five specific mechanisms by which flame retardancy may occur: physical dilution, chemical interaction, inert gas dilution, thermal quenching, and protective coatings.

A principal object of the invention is to provide an igniter composition or device having all of the desirable characteristics of a starter mixture including high stability, easy ignition, a sufficiently high spontaneous ignition temperature to avoid accidental self-ignition, a high burning temperature, flameless ignition, a low weight, a low cost, and ease of manufacture. The igniter composition of the present invention will not exhibit any substantial brisance; that is, upon ignition, the igniter composition will not react with a deleterious shock or explosions that would tend to disintegrate portions of the main filling composition.

Such a pyrotechnic ignition composition, when used in the manufacture of ignition elements employed for the initiation of pyrotechnic filling, provides the ignition elements with a desired burning rate. The burning rate of the igniter composition or devices must be uniform and controllable to produce the ignition products over a period sufficient to ignite all exposed burning surfaces of the pyrotechnic main filling.

A process for producing a pyrotechnic ignition composition of the current invention is disclosed, the process including the steps of:

-   -   mixing an oxidizer, a fuel, a flame suppressant additive, a         thickener/surfactant/dispersant, and a liquid, to form a paste         or slurry;     -   impregnating a tailored shape of absorbent web material in this         paste or slurry and draying to remove the liquid.     -   optionally, drying the paste or slurry to remove the liquid and         to obtain a solid product, which can be used by itself, or if         necessary, rendering the solid product into particulate form.

The paste or slurry of this invention is formed by mixing a solid phase with a liquid phase.

-   -   A solid phase consisting of and oxidizer and fuel.     -   liquid phase consisting of water, the         thickener/surfactant/dispersant, and the flame suppressant         additive.

The liquid may be an organic liquid such as a solvent. Instead, the liquid may be water, which is preferred for this invention. Water may comprise 15-45% by mass of the composition, preferred 17-41% by mass of the composition.

Typically, in the manufacture of pyrotechnic ignition compositions or devices of the kind in question by a process of the type to which the present invention relates, the exact oxidizer and fuel constituents, their particle sizes, and their proportions in the paste or slurry mixture are selected in accordance with practical and economic considerations, bearing in mind safety and the intended use of the ignition compositions or devices.

The oxidizer may be in solid particulate form. The preferred oxidizer is potassium nitrate and the oxidizer may comprise 25-50% by mass of the composition, preferred 30-45% by mass of the composition.

The fuel may also be in solid particulate form. The fuel may comprise silicon and charcoal (carbon). The fuel may comprise 20-30% by mass of the composition, preferred 22-28% by mass of the composition. To ensure ignition of the starter mixture it is preferred that the particle size of the starter mixture be such that all the material passes a No. 200 U.S. Standard Sieve and much of it passes a No. 325 U.S. Standard Sieve.

The silicon should have a sufficiently small particle size that at least 50% and preferably, 75% of it will pass through a No. 200 U.S. Standard Sieve. Silicon may comprise 20-30% by mass of the composition, with 22-26% by mass of the composition being preferred.

In accordance with present invention, the ignition composition contains from 2 to 10% of granular amorphous carbon that exhibits conchoidal fracture and which preferably passes a 100-mesh screen. The preferred quantity is from 2.0 to 4% by mass of the composition. Anthracite coal with a high fixed carbon content is preferred and representative of a type of amorphous carbon that exhibits conchoidal fracture. In the context of the specification, “a material that exhibits conchoidal fracture” means a material that when shattered forms a jagged particle, with shattering occurring so that typically concave areas are developed in addition very sharp edges.

By using a precise amount of a flame suppressant additive (a heat-absorbing compound that acts as an oxygen scavenger), the flame-producing ability of the ignition mixture can be controlled in order to prevent possible safety issues. Guanidine is very soluble in water, and any of the water-soluble salts of guanidine can be used as flame suppressant additives in the present invention. For example, guanidine hydrochloride, guanidine acetate, and guanidine sulfate are very soluble in water. In addition, guanidine carbonate, guanidine thiocyanate and guanidine nitrate are sufficiently soluble in water to permit their use as flame suppressant additives in the present invention. Guanidine carbonate is a particularly desirable guanidine compound for use as a flame suppressant additive in the present invention.

The guanidine water soluble salts mentioned above, preferably guanidine carbonate, may comprise 2 to 5% by mass of the composition, with 2 to 4% by mass of the composition being preferred. It is known that guanidine salts can be used as thickening agents, and for this particular embodiment, they generate less polysaccharide-thickener consumption. The increased viscosity is thought to be caused by the ionic effect of the guanidine salt on the polysaccharide molecule, causing increased rigidity in the molecule's backbone. Hydrogen bonding between rigid molecular backbones is thought to increase intermolecular ordering, causing increased viscosity.

Polysaccharides employed in the aqueous fluid utilized in this invention include the scleroglucan group of homopolysaccharides, xanthan gum heteropolysaccharides, and the preferred is galactomannan, particularly guar gum.

Scleroglucan, also known as poly (glucosylglucan), is produced by submerged aerobic fermentation of D-glucose by a selected species of the Sclerotium fungus. The nonionic polymer consists of a linear chain of anhydroglucose units linked beta one to three and has a molecular weight ranging from 500,000 to over 6,000,000. Thirty to thirty-five percent of the linear chain units bear single appended anhydroglucose units linked beta one to six. A satisfactory scleroglucan for the practice of this invention is Actigum CS-11 ® (formerly known as Polytran®) from Ceca, S. A. in Paris, France.

Xanthan gum heteropolysaccharides suitable for use in this invention are produced by the fermentation of carbohydrates by the Xanthomonas campestris microorganism. The anionic polymer consists of repeating units of D-glucose, D-mannose, and D-glucuronic acid and has a molecular weight ranging from U.S. Pat. No. 1,000,000 to over 6,000,000. Glucose linkages like those of cellulose make up the polymer backbone. Mannose and glucuronic acid units are in the side chains, and some mannose units are modified with acetyl or pyruvic ketal groups. A satisfactory xanthan gum for the practice of this invention is Rhodopol 23-R® from RhonePoulenc in Monmouth Junction, N.J. 08852.

Guar gum is a polysaccharide composed of the sugars galactose and mannose. The backbone is a linear chain of β1,4-linked mannose residues to which galactose residues are 1,6-linked at every second mannose, forming short side-branches. Guar gum may comprise 1-7% by mass of the composition, preferred 4.5-6% by mass of the composition.

The surface-active or surfactant agent may be in particulate form, and may be a wetting agent and/or a rheology modifier and/or a dispersant. The surfactant may be selected from the so-called non-ionic surfactants, anionic surfactants and cationic surfactants. The surfactant may thus comprise an acrylic ester, a styrene polymer, and/or an acrylic copolymer, which are all wetting agents; and/or a polyethylene glycol, a powdered smectite clay, carboxymethyl cellulose, polyvinyl alcohol and/or polyvinyl pyrrolidone, which are rheology modifiers or thickeners. The preferred surfactant for this invention is an organic compound derived from sucroglycerides of edible vegetable oil, which act as a biosurfactant-dispersant for mineral slurries. The representative trade name for this product is Sucrol from Tensac s.h. Argentina. The surfactant-dispersant may be in the form of an aqueous dispersion with guanidine soluble salt used as flameless additive but acting also as a cross-linking agent for a type of surfactant-dispersant, such as guanidine carbonate, when admixed with the oxidizer and the fuel. The surfactant-dispersant may comprise 0.25% to 3%, by mass, of the paste or slurry before drying, i.e. on a wet basis. Typically, the surfactant-dispersant may comprise 0.5% to 2%, by mass, of the paste or slurry. Thus, the composition may comprise:

Oxidizer 25-50% Fuel 20-30% Flameless additive  2-5% Thickener/Surfactant/Dispersant 0.5-10% 

Combining guanidine soluble salts with such rheology modifiers and suitable oxidant and fuel achieves a tailored ignition composition or device that will flamelessly ignite and produce hot slag, as well as demonstrate a high burning rate giving the required ignition time. Such an ignition composition also resists so-called sedimentation or separation of the constituents of the paste or slurry, after it is formulated and before it is dried.

The paste or slurry is typically used to impregnate a shape (typically, such shapes include cup shapes, cylindrical shapes, hemispherical shapes, rectangular shapes, etc. or any shape, normally dictated by the end use, can be employed) of absorbent web material, such as light weight cotton (cambric), uncoated fiberglass, or open cell foams, and then subsequently dried to remove the liquid.

Open cell structured foams contain pores that are connected to each other and form an interconnected network which is relatively soft. A reticulated, open-pore, flexible, ester-type of polyurethane foam, characterized by a skeletal structure of strands which provide a constant 97 percent void space and a very high degree of permeability, will be filled with the slurry or paste composition when immersed. Foam rubber refers to rubber that has been manufactured with a foaming agent to create an air-filled matrix structure. However, preferred cellular materials are the synthetic organic polymeric foams, for example, polystyrene, polyurethane, polyethylene, polypropylene, polyvinyl chloride, polybutadiene, rubber or copolymers of these materials with other polymeric substances. Most preferred are polystyrene foam and polyurethane foam. The size of the cells, the distribution of various sizes of cells and the degree of expansion is not especially critical; thus, for example suitable foams may have a density ranging from 0.3 to 5 lbs. per cubic foot, preferably from 1 to 4 lbs. per cubic foot.

The invention will now be described, by way of non-limiting illustrative example, with reference to the following examples:

Example 1

Pyrotechnic ignition compositions, in accordance with the invention, were formulated having the following compositions (proportions expressed as % by mass):

Constituent A B Potassium Nitrate (oxidizer) 31.00 ± 0.25 31.00 ± 0.25 Silicon (fuel) 22.00 ± 0.25 22.00 ± 0.25 Charcoal (fuel)  2.20 ± 0.25  2.20 ± 0.25 Guar Gum (thickener)  4.00 ± 0.25  4.00 ± 0.25 Guanidine Carbonate (flame suppressant)  3.50 ± 0.25 Guanidine Nitrate (flame suppressant)  3.00 ± 0.25 Water (solvent) 37.30 ± 0.25 37.80 ± 0.25 100.00 100.00

Referring now to FIG. 1, the pyrotechnic delay compositions were produced as follows: The process starts (12) by weighing (14) a quantity of powdered polysaccharide as guar gum 16, a quantity of distilled water 18, a quantity of oxidizer 20, a quantity of fuel 22, and a quantity of guanidine salts 24. The guar gum is a soft, bulky powder that contains from about 30-90% by weight of active polysaccharide. The powder must be fully hydrated with the water (26) prior to mixing with guanidine salts as a first mixing step (28) and in a second mixing step (30) with oxidizer and fuel to obtain a slurry or paste. Any commercially available blender can be used in this process, such as ribbon blenders, signia-blade dough mixers, tumble blenders and the like. A tumble blender is preferred because it will impart at least moderate shear action to the tumbling charge.

In one embodiment of the process, shapes are cut (32), and the slurry is then used to impregnate the shapes made of an absorbent web, preferably open cell foam rubber, via soaking and squeezing (34). Subsequently, the impregnated shapes are dried (36) to reduce their water content to less than 1%, by mass to create a solid product. At least one shape is subjected to an ignition/burning test (38) to confirm the shapes have the desired qualities, which completes the process (40).

In an alternative embodiment of the process, the slurry is oven dried (42) to a consistency that allows hand granulation by pushing the dried product through a 1 mm screen (44). Thereafter, the resultant granules are further dried (36) to reduce their water content to less than 1%, by mass to create a solid product. A portion of the granules is subjected to an ignition/burning test (38) to confirm the granules have the desired qualities, which completes the process (40).

Example 2

Pyrotechnic ignition compositions, in accordance with the invention, were formulated having the following compositions (proportions expressed as % by mass):

Constituent A B Potassium Nitrate (oxidizer) 32.50 ± 0.25 32.50 ± 0.25 Silicon (fuel) 22.50 ± 0.25 22.50 ± 0.25 Charcoal (fuel)  2.50 ± 0.25  2.50 ± 0.25 Sucrol (surfactant-dispersant)  1.00 ± 0.25 Smectite clay particles (VEEGUM/  0.50 ± 0.25 VAN GEL) (rheology modifier/thickener) Guanidine Carbonate (flame suppressant)  3.50 ± 0.25  3.50 ± 0.25 Water (solvent) 38.00 ± 0.25 38.50 ± 0.25 100.00 100.00

The Sucrol was obtained from Tensac s.h. Viamonte 1376 4000-San M. Tucuman-Argentina. Veegum/Van Gel were obtained from R.T. Vanderbilt Company, Inc. 30 Winfield Street, Norwalk, Conn. 06855.

The pyrotechnic ignition composition or device was produced in the same manner as that of Example 1.

The flame retardant within the pyrotechnic ignition composition of the current invention modifies the burning characteristics of the composition in several desirable ways. First, the flame retardant ensures the burning of the composition proceeds at the proper rate of speed to give the desired ignition time of the main filling composition. Second, the flame retardant ensures the composition burns without a visible flame. Third, the flame retardant does not prevent the burning composition from producing a flame and slag products that are hot enough to ignite the main filling composition. As an additional benefit, the flame retardant is a clean, effective, non-toxic, non-ozone depleting, non-halogenated compound.

The use of a flame retardant within the pyrotechnic ignition composition of the current invention is counterintuitive for two reasons. First, the goal of a pyrotechnic ignition composition is to burn with sufficient intensity to ignite the main filling composition, so the use of an ingredient that impedes burning is contraindicated. Second, guanidine salts, such as guanidine nitrate, are conventionally employed in the art of ignition as an exothermic reactant in a smoke grenade (U.S. Pat. No. 4,238,254), or as an additional fuel for a flare igniter (U.S. Pat. No. 6,170,399). This makes their usage in the current invention for their flame retardant properties nonobvious.

While current embodiments of a flameless igniting slurry composition and methods of preparation have been described in detail, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention.

With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.

Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. 

I claim:
 1. A pyrotechnic flameless ignition composition comprising: an oxidizer; a fuel; a flame retardant; a liquid; and a rheology modifier.
 2. The composition of claim 1 wherein the rheology modifier is in particulate form.
 3. The composition of claim 1 wherein the rheology modifier is at least one of the group consisting of polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, polysaccharides, sucroglycerides of edible vegetable oil, and powdered smectite clay.
 4. The composition of claim 1 wherein the flame retardant is in particulate form.
 5. The composition of claim 1 wherein the flame retardant is a water-soluble salt.
 6. The composition of claim 5 wherein the water-soluble salt is at least one of the group consisting of guanidine hydrochloride, guanidine acetate, guanidine sulfate, guanidine carbonate, guanidine thiocyanate, guanidine nitrate, and guanidine carbonate.
 7. The composition of claim 1 wherein the liquid is an organic solvent.
 8. The composition of claim 1 wherein the liquid is water.
 9. The composition of claim 1 wherein the oxidizer is potassium nitrate.
 10. The composition of claim 1 wherein the fuel is at least one of the group consisting of silicon and charcoal.
 11. The composition of claim 1 wherein the composition comprises on a mass basis oxidizer 25-50%, fuel 20-30%, flame retardant 2-5%, and rheology modifier 0.5-10%.
 12. A pyrotechnic ignition device comprising a shape of absorbent web material impregnated with the composition of claim 1 in a dried state.
 13. The device of claim 12 wherein the absorbent web material is selected from the group consisting of cambric, uncoated fiberglass, and open cell foams made of polystyrene, polyurethane, polyethylene, polypropylene, polyvinyl chloride, polybutadiene, rubber and copolymers of these materials with other polymeric substances.
 14. A pyrotechnic ignition device comprising the composition of claim 1 in a dried, particulate form.
 15. A process for producing a pyrotechnic flameless ignition composition comprising the steps of: obtaining a quantity of oxidizer; obtaining a quantity of fuel; obtaining a quantity of flame retardant; obtaining a quantity of liquid; obtain a quantity of rheology modifier; adding the quantity of rheology modifier to the quantity of liquid to form a dispersion; adding the quantity of flame retardant to the dispersion to form a first mixture; and adding the quantity of oxidizer and the quantity of fuel to the first mixture to form a second mixture.
 16. The process of claim 15 further comprising the steps of: obtaining a shape of absorbent web material; impregnating the web material with the second mixture; and drying the impregnated web material until the impregnated web material is solid.
 17. The process of claim 15 further comprising the steps of: partially drying the second mixture; rendering the partially dried second mixture into particulate form; and drying the particulates until they are solid.
 18. The process of claim 15 wherein the first mixture is an aqueous dispersion.
 19. The process of claim 15 wherein the second mixture is a slurry.
 20. The process of claim 15 wherein the second mixture comprises on a mass basis oxidizer 25-50%, fuel 20-30%, flame retardant 2-5%, and rheology modifier 0.5-10%.
 21. The process of claim 16 wherein the shape is selected from the group consisting of cup shapes, cylindrical shapes, hemispherical shapes, and rectangular shapes.
 22. The process of claim 16 wherein the absorbent web material is selected from the group consisting of cambric, uncoated fiberglass, and open cell foams made of polystyrene, polyurethane, polyethylene, polypropylene, polyvinyl chloride, polybutadiene, rubber and copolymers of these materials with other polymeric substances. 